/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/ShapeFunctions.h
Find the point on the faces of the Box that is closest to the input Point. If the Point is inside the Box, it is returned, ie points Inside do not project to the Box Faces
static FVector FindClosestPointOnBox ( FBox Box, FVector Point, bool & bIsInside )